CVE-2026-48859

Description

Observable Timing Discrepancy vulnerability in Erlang/OTP ssh (ssh_auth, ssh_options modules) allows unauthenticated remote username enumeration via timing side-channel in password authentication. When the SSH daemon is configured with the user_passwords or password option, ssh_auth:check_password/3 performs a PBKDF2-SHA256 computation with 600,000 iterations (~300ms) for valid usernames, but returns immediately (~0ms) for invalid usernames via the ssh_options:get_password_option/2 path. This timing difference is detectable in a single authentication attempt and allows an unauthenticated attacker to distinguish valid from invalid usernames. The user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability. This vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl. This issue affects OTP from OTP 29.0 before 29.0.2 corresponding to ssh from 6.0 before 6.0.1.

PUBLISHED Reserved 2026-05-25 | Published 2026-06-10 | Updated 2026-06-10 | Assigner EEF

Problem types

CWE-208 Observable Timing Discrepancy

Product status

Credits

Zhang Delong finder

Jakub Witczak remediation developer

Ingela Anderton Andin remediation reviewer

Michał Wąsowski remediation reviewer

References

github.com/...ng/otp/security/advisories/GHSA-3w6p-vwhf-wvp4 vendor-advisory related

cna.erlef.org/cves/CVE-2026-48859.html related

osv.dev/vulnerability/EEF-CVE-2026-48859 related

www.erlang.org/doc/system/versions.html

github.com/...ommit/c342092ef4b369bb409d5b71ac8fd83bab74aedf patch

cve.org (CVE-2026-48859)

nvd.nist.gov (CVE-2026-48859)

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